This invention relates to a dump block for a dragline bucket and, more particularly, to a dump block featuring novel and advantageous plastic journals.
The dump block is provided as part of the rigging of a dragline and is employed in lifting and carrying the bucket, then allowing the bucket to dump when the drag chains are slacked. The dump block has reeved or threaded therein a rope (generally heavy-duty wire rope) and this rope normally wears out on the order of 2-4 weeks of operation. This short life span causes increased costs for the dragline operators, viz., mines, etc. in two areas: (1) the cost of the rope can be quite expensive if the operators are not able to use the worn drag or hoist rope and (2) there is the cost of down-time associated with changing the ropes this frequently.
For a sizable bucket, the normal dump block can be approximately 48" in diameter which has a pin at the center of approximately 5" diameter. The pin normally carries a tapered roller bearing which is not only extremely expensive because of the highly machined parts but also wears out quickly and is an area of high maintenance. To operate the conventional dump block, the tapered roller bearings should be continually checked and tightened to insure proper preload on the bearings. When this is not done, the bearing fails prematurely.
According to the invention, a dump block is provided which has a sizable increase in bearing surface thereby reducing the wear and loads on the bearing. To achieve this, and simultaneously achieve the goal of easy maintenance, a significantly larger center pin is provided in the form of a hollow pipe which doubles as an oil reservoir. By reducing the loads on the bearing, we are able to employ plastic journals and most advantageously in the form of arcuate segments disposed inwardly and outwardly of a steel annulus.
A number of advantages accrue from the invention which include: (1) reduction of the weight of the entire dump block assembly to enable the machine to carry more dirt, or to allow for the addition of more weight at a wear area on the bucket; (2) increase of the dump rope life by the addition of plastic rope groove segments so that the rope wear life can be much as doubled or tripled; (3) increase of the life of the bearing through the use of plastic bearing inserts which require low maintenance and are inexpensive to replace; (4) the addition of an oil reservoir for continual oiling of the plastic bearings to reduce friction; and (5) reduction of the down-time by making all of these parts quick and easy to change and replace. All of the foregoing advantages contribute to a reduction in the overall cost of the dump block and, more importantly, the operation of the overall machine.
Other objects and advantages of the invention may be seen in the details of the ensuing specification.